annotate hotspot/src/share/vm/runtime/safepoint.cpp @ 35492:c8c0273e6b91

8146690: Make all classes in GC follow the naming convention. Reviewed-by: dholmes, stefank
author david
date Thu, 14 Jan 2016 13:26:19 +0100
parents be6025ebffea
children 5aa55674a362
rev   line source
duke@1 1 /*
pliden@30764 2 * Copyright (c) 1997, 2015, Oracle and/or its affiliates. All rights reserved.
duke@1 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
duke@1 4 *
duke@1 5 * This code is free software; you can redistribute it and/or modify it
duke@1 6 * under the terms of the GNU General Public License version 2 only, as
duke@1 7 * published by the Free Software Foundation.
duke@1 8 *
duke@1 9 * This code is distributed in the hope that it will be useful, but WITHOUT
duke@1 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
duke@1 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
duke@1 12 * version 2 for more details (a copy is included in the LICENSE file that
duke@1 13 * accompanied this code).
duke@1 14 *
duke@1 15 * You should have received a copy of the GNU General Public License version
duke@1 16 * 2 along with this work; if not, write to the Free Software Foundation,
duke@1 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
duke@1 18 *
trims@5547 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
trims@5547 20 * or visit www.oracle.com if you need additional information or have any
trims@5547 21 * questions.
duke@1 22 *
duke@1 23 */
duke@1 24
stefank@7397 25 #include "precompiled.hpp"
gziemski@24426 26 #include "classfile/stringTable.hpp"
mgronlun@34666 27 #include "classfile/symbolTable.hpp"
stefank@7397 28 #include "classfile/systemDictionary.hpp"
stefank@7397 29 #include "code/codeCache.hpp"
stefank@7397 30 #include "code/icBuffer.hpp"
stefank@7397 31 #include "code/nmethod.hpp"
stefank@7397 32 #include "code/pcDesc.hpp"
stefank@7397 33 #include "code/scopeDesc.hpp"
pliden@30764 34 #include "gc/shared/collectedHeap.hpp"
pliden@30764 35 #include "gc/shared/gcLocker.inline.hpp"
stefank@7397 36 #include "interpreter/interpreter.hpp"
rprotacio@33763 37 #include "logging/log.hpp"
stefank@7397 38 #include "memory/resourceArea.hpp"
stefank@7397 39 #include "memory/universe.inline.hpp"
stefank@7397 40 #include "oops/oop.inline.hpp"
coleenp@8076 41 #include "oops/symbol.hpp"
goetz@25351 42 #include "runtime/atomic.inline.hpp"
stefank@7397 43 #include "runtime/compilationPolicy.hpp"
stefank@7397 44 #include "runtime/deoptimization.hpp"
stefank@7397 45 #include "runtime/frame.inline.hpp"
stefank@7397 46 #include "runtime/interfaceSupport.hpp"
stefank@7397 47 #include "runtime/mutexLocker.hpp"
goetz@24351 48 #include "runtime/orderAccess.inline.hpp"
stefank@7397 49 #include "runtime/osThread.hpp"
stefank@7397 50 #include "runtime/safepoint.hpp"
stefank@7397 51 #include "runtime/signature.hpp"
stefank@7397 52 #include "runtime/stubCodeGenerator.hpp"
stefank@7397 53 #include "runtime/stubRoutines.hpp"
stefank@7397 54 #include "runtime/sweeper.hpp"
stefank@7397 55 #include "runtime/synchronizer.hpp"
stefank@14583 56 #include "runtime/thread.inline.hpp"
stefank@7397 57 #include "services/runtimeService.hpp"
stefank@7397 58 #include "utilities/events.hpp"
jprovino@15482 59 #include "utilities/macros.hpp"
jprovino@15482 60 #if INCLUDE_ALL_GCS
pliden@30764 61 #include "gc/cms/concurrentMarkSweepThread.hpp"
pliden@30764 62 #include "gc/g1/suspendibleThreadSet.hpp"
jprovino@15482 63 #endif // INCLUDE_ALL_GCS
stefank@7397 64 #ifdef COMPILER1
stefank@7397 65 #include "c1/c1_globals.hpp"
stefank@7397 66 #endif
duke@1 67
duke@1 68 // --------------------------------------------------------------------------------------------------
duke@1 69 // Implementation of Safepoint begin/end
duke@1 70
duke@1 71 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
duke@1 72 volatile int SafepointSynchronize::_waiting_to_block = 0;
duke@1 73 volatile int SafepointSynchronize::_safepoint_counter = 0;
never@11631 74 int SafepointSynchronize::_current_jni_active_count = 0;
xlu@5042 75 long SafepointSynchronize::_end_of_last_safepoint = 0;
duke@1 76 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
duke@1 77 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
duke@1 78 static bool timeout_error_printed = false;
duke@1 79
duke@1 80 // Roll all threads forward to a safepoint and suspend them all
duke@1 81 void SafepointSynchronize::begin() {
duke@1 82
duke@1 83 Thread* myThread = Thread::current();
duke@1 84 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
duke@1 85
xlu@5042 86 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
xlu@5042 87 _safepoint_begin_time = os::javaTimeNanos();
xlu@5042 88 _ts_of_current_safepoint = tty->time_stamp().seconds();
xlu@5042 89 }
duke@1 90
jprovino@15482 91 #if INCLUDE_ALL_GCS
duke@1 92 if (UseConcMarkSweepGC) {
duke@1 93 // In the future we should investigate whether CMS can use the
duke@1 94 // more-general mechanism below. DLD (01/05).
duke@1 95 ConcurrentMarkSweepThread::synchronize(false);
ysr@3262 96 } else if (UseG1GC) {
pliden@24094 97 SuspendibleThreadSet::synchronize();
duke@1 98 }
jprovino@15482 99 #endif // INCLUDE_ALL_GCS
duke@1 100
duke@1 101 // By getting the Threads_lock, we assure that no threads are about to start or
duke@1 102 // exit. It is released again in SafepointSynchronize::end().
duke@1 103 Threads_lock->lock();
duke@1 104
duke@1 105 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
duke@1 106
duke@1 107 int nof_threads = Threads::number_of_threads();
duke@1 108
rprotacio@33763 109 log_debug(safepoint)("Safepoint synchronization initiated. (%d)", nof_threads);
duke@1 110
duke@1 111 RuntimeService::record_safepoint_begin();
duke@1 112
duke@1 113 MutexLocker mu(Safepoint_lock);
duke@1 114
never@11631 115 // Reset the count of active JNI critical threads
never@11631 116 _current_jni_active_count = 0;
never@11631 117
duke@1 118 // Set number of threads to wait for, before we initiate the callbacks
duke@1 119 _waiting_to_block = nof_threads;
duke@1 120 TryingToBlock = 0 ;
duke@1 121 int still_running = nof_threads;
duke@1 122
duke@1 123 // Save the starting time, so that it can be compared to see if this has taken
duke@1 124 // too long to complete.
goetz@33589 125 jlong safepoint_limit_time = 0;
duke@1 126 timeout_error_printed = false;
duke@1 127
xlu@4006 128 // PrintSafepointStatisticsTimeout can be specified separately. When
xlu@4006 129 // specified, PrintSafepointStatistics will be set to true in
xlu@4006 130 // deferred_initialize_stat method. The initialization has to be done
xlu@4006 131 // early enough to avoid any races. See bug 6880029 for details.
xlu@4006 132 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
xlu@4006 133 deferred_initialize_stat();
xlu@4006 134 }
xlu@4006 135
duke@1 136 // Begin the process of bringing the system to a safepoint.
duke@1 137 // Java threads can be in several different states and are
duke@1 138 // stopped by different mechanisms:
duke@1 139 //
duke@1 140 // 1. Running interpreted
jwilhelm@22551 141 // The interpreter dispatch table is changed to force it to
duke@1 142 // check for a safepoint condition between bytecodes.
duke@1 143 // 2. Running in native code
duke@1 144 // When returning from the native code, a Java thread must check
duke@1 145 // the safepoint _state to see if we must block. If the
duke@1 146 // VM thread sees a Java thread in native, it does
duke@1 147 // not wait for this thread to block. The order of the memory
duke@1 148 // writes and reads of both the safepoint state and the Java
duke@1 149 // threads state is critical. In order to guarantee that the
duke@1 150 // memory writes are serialized with respect to each other,
duke@1 151 // the VM thread issues a memory barrier instruction
duke@1 152 // (on MP systems). In order to avoid the overhead of issuing
duke@1 153 // a memory barrier for each Java thread making native calls, each Java
duke@1 154 // thread performs a write to a single memory page after changing
duke@1 155 // the thread state. The VM thread performs a sequence of
duke@1 156 // mprotect OS calls which forces all previous writes from all
duke@1 157 // Java threads to be serialized. This is done in the
duke@1 158 // os::serialize_thread_states() call. This has proven to be
duke@1 159 // much more efficient than executing a membar instruction
duke@1 160 // on every call to native code.
duke@1 161 // 3. Running compiled Code
duke@1 162 // Compiled code reads a global (Safepoint Polling) page that
duke@1 163 // is set to fault if we are trying to get to a safepoint.
duke@1 164 // 4. Blocked
duke@1 165 // A thread which is blocked will not be allowed to return from the
duke@1 166 // block condition until the safepoint operation is complete.
duke@1 167 // 5. In VM or Transitioning between states
duke@1 168 // If a Java thread is currently running in the VM or transitioning
duke@1 169 // between states, the safepointing code will wait for the thread to
duke@1 170 // block itself when it attempts transitions to a new state.
duke@1 171 //
duke@1 172 _state = _synchronizing;
duke@1 173 OrderAccess::fence();
duke@1 174
duke@1 175 // Flush all thread states to memory
duke@1 176 if (!UseMembar) {
duke@1 177 os::serialize_thread_states();
duke@1 178 }
duke@1 179
duke@1 180 // Make interpreter safepoint aware
duke@1 181 Interpreter::notice_safepoints();
duke@1 182
shade@27662 183 if (DeferPollingPageLoopCount < 0) {
duke@1 184 // Make polling safepoint aware
duke@1 185 guarantee (PageArmed == 0, "invariant") ;
duke@1 186 PageArmed = 1 ;
duke@1 187 os::make_polling_page_unreadable();
duke@1 188 }
duke@1 189
duke@1 190 // Consider using active_processor_count() ... but that call is expensive.
duke@1 191 int ncpus = os::processor_count() ;
duke@1 192
duke@1 193 #ifdef ASSERT
duke@1 194 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
duke@1 195 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
never@12108 196 // Clear the visited flag to ensure that the critical counts are collected properly.
never@12108 197 cur->set_visited_for_critical_count(false);
duke@1 198 }
duke@1 199 #endif // ASSERT
duke@1 200
duke@1 201 if (SafepointTimeout)
duke@1 202 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
duke@1 203
duke@1 204 // Iterate through all threads until it have been determined how to stop them all at a safepoint
duke@1 205 unsigned int iterations = 0;
duke@1 206 int steps = 0 ;
duke@1 207 while(still_running > 0) {
duke@1 208 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
duke@1 209 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
duke@1 210 ThreadSafepointState *cur_state = cur->safepoint_state();
duke@1 211 if (cur_state->is_running()) {
duke@1 212 cur_state->examine_state_of_thread();
duke@1 213 if (!cur_state->is_running()) {
duke@1 214 still_running--;
duke@1 215 // consider adjusting steps downward:
duke@1 216 // steps = 0
duke@1 217 // steps -= NNN
duke@1 218 // steps >>= 1
duke@1 219 // steps = MIN(steps, 2000-100)
duke@1 220 // if (iterations != 0) steps -= NNN
duke@1 221 }
rprotacio@33763 222 if (log_is_enabled(Trace, safepoint)) {
rprotacio@33763 223 ResourceMark rm;
rprotacio@33763 224 cur_state->print_on(LogHandle(safepoint)::debug_stream());
rprotacio@33763 225 }
duke@1 226 }
duke@1 227 }
duke@1 228
xlu@4006 229 if (PrintSafepointStatistics && iterations == 0) {
duke@1 230 begin_statistics(nof_threads, still_running);
duke@1 231 }
duke@1 232
duke@1 233 if (still_running > 0) {
duke@1 234 // Check for if it takes to long
duke@1 235 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
duke@1 236 print_safepoint_timeout(_spinning_timeout);
duke@1 237 }
duke@1 238
duke@1 239 // Spin to avoid context switching.
duke@1 240 // There's a tension between allowing the mutators to run (and rendezvous)
duke@1 241 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
duke@1 242 // a mutator might otherwise use profitably to reach a safepoint. Excessive
duke@1 243 // spinning by the VM thread on a saturated system can increase rendezvous latency.
duke@1 244 // Blocking or yielding incur their own penalties in the form of context switching
duke@1 245 // and the resultant loss of $ residency.
duke@1 246 //
duke@1 247 // Further complicating matters is that yield() does not work as naively expected
duke@1 248 // on many platforms -- yield() does not guarantee that any other ready threads
fparain@25333 249 // will run. As such we revert to naked_short_sleep() after some number of iterations.
fparain@25333 250 // nakes_short_sleep() is implemented as a short unconditional sleep.
duke@1 251 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
duke@1 252 // can actually increase the time it takes the VM thread to detect that a system-wide
duke@1 253 // stop-the-world safepoint has been reached. In a pathological scenario such as that
duke@1 254 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
duke@1 255 // In that case the mutators will be stalled waiting for the safepoint to complete and the
duke@1 256 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
duke@1 257 // will eventually wake up and detect that all mutators are safe, at which point
duke@1 258 // we'll again make progress.
duke@1 259 //
duke@1 260 // Beware too that that the VMThread typically runs at elevated priority.
duke@1 261 // Its default priority is higher than the default mutator priority.
duke@1 262 // Obviously, this complicates spinning.
duke@1 263 //
duke@1 264 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
duke@1 265 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
duke@1 266 //
duke@1 267 // See the comments in synchronizer.cpp for additional remarks on spinning.
duke@1 268 //
duke@1 269 // In the future we might:
jwilhelm@22551 270 // 1. Modify the safepoint scheme to avoid potentially unbounded spinning.
duke@1 271 // This is tricky as the path used by a thread exiting the JVM (say on
duke@1 272 // on JNI call-out) simply stores into its state field. The burden
duke@1 273 // is placed on the VM thread, which must poll (spin).
duke@1 274 // 2. Find something useful to do while spinning. If the safepoint is GC-related
duke@1 275 // we might aggressively scan the stacks of threads that are already safe.
duke@1 276 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
duke@1 277 // If all the mutators are ONPROC there's no reason to sleep or yield.
duke@1 278 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
duke@1 279 // 5. Check system saturation. If the system is not fully saturated then
duke@1 280 // simply spin and avoid sleep/yield.
duke@1 281 // 6. As still-running mutators rendezvous they could unpark the sleeping
duke@1 282 // VMthread. This works well for still-running mutators that become
duke@1 283 // safe. The VMthread must still poll for mutators that call-out.
duke@1 284 // 7. Drive the policy on time-since-begin instead of iterations.
duke@1 285 // 8. Consider making the spin duration a function of the # of CPUs:
duke@1 286 // Spin = (((ncpus-1) * M) + K) + F(still_running)
duke@1 287 // Alternately, instead of counting iterations of the outer loop
duke@1 288 // we could count the # of threads visited in the inner loop, above.
duke@1 289 // 9. On windows consider using the return value from SwitchThreadTo()
duke@1 290 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
duke@1 291
shade@27662 292 if (int(iterations) == DeferPollingPageLoopCount) {
duke@1 293 guarantee (PageArmed == 0, "invariant") ;
duke@1 294 PageArmed = 1 ;
duke@1 295 os::make_polling_page_unreadable();
duke@1 296 }
duke@1 297
duke@1 298 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
duke@1 299 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
duke@1 300 ++steps ;
duke@1 301 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
duke@1 302 SpinPause() ; // MP-Polite spin
duke@1 303 } else
duke@1 304 if (steps < DeferThrSuspendLoopCount) {
fparain@25477 305 os::naked_yield() ;
duke@1 306 } else {
fparain@25333 307 os::naked_short_sleep(1);
duke@1 308 }
duke@1 309
duke@1 310 iterations ++ ;
duke@1 311 }
duke@1 312 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
duke@1 313 }
duke@1 314 assert(still_running == 0, "sanity check");
duke@1 315
duke@1 316 if (PrintSafepointStatistics) {
duke@1 317 update_statistics_on_spin_end();
duke@1 318 }
duke@1 319
duke@1 320 // wait until all threads are stopped
duke@1 321 while (_waiting_to_block > 0) {
rprotacio@33763 322 log_debug(safepoint)("Waiting for %d thread(s) to block", _waiting_to_block);
duke@1 323 if (!SafepointTimeout || timeout_error_printed) {
duke@1 324 Safepoint_lock->wait(true); // true, means with no safepoint checks
duke@1 325 } else {
duke@1 326 // Compute remaining time
duke@1 327 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
duke@1 328
duke@1 329 // If there is no remaining time, then there is an error
duke@1 330 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
duke@1 331 print_safepoint_timeout(_blocking_timeout);
duke@1 332 }
duke@1 333 }
duke@1 334 }
duke@1 335 assert(_waiting_to_block == 0, "sanity check");
duke@1 336
duke@1 337 #ifndef PRODUCT
duke@1 338 if (SafepointTimeout) {
duke@1 339 jlong current_time = os::javaTimeNanos();
duke@1 340 if (safepoint_limit_time < current_time) {
duke@1 341 tty->print_cr("# SafepointSynchronize: Finished after "
duke@1 342 INT64_FORMAT_W(6) " ms",
duke@1 343 ((current_time - safepoint_limit_time) / MICROUNITS +
gziemski@33222 344 (jlong)SafepointTimeoutDelay));
duke@1 345 }
duke@1 346 }
duke@1 347 #endif
duke@1 348
duke@1 349 assert((_safepoint_counter & 0x1) == 0, "must be even");
duke@1 350 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
duke@1 351 _safepoint_counter ++;
duke@1 352
duke@1 353 // Record state
duke@1 354 _state = _synchronized;
duke@1 355
duke@1 356 OrderAccess::fence();
duke@1 357
never@12108 358 #ifdef ASSERT
never@12108 359 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
never@12108 360 // make sure all the threads were visited
never@12108 361 assert(cur->was_visited_for_critical_count(), "missed a thread");
never@12108 362 }
never@12108 363 #endif // ASSERT
never@12108 364
never@11631 365 // Update the count of active JNI critical regions
david@35492 366 GCLocker::set_jni_lock_count(_current_jni_active_count);
never@11631 367
rprotacio@33763 368 if (log_is_enabled(Debug, safepoint)) {
duke@1 369 VM_Operation *op = VMThread::vm_operation();
rprotacio@33763 370 log_debug(safepoint)("Entering safepoint region: %s",
rprotacio@33763 371 (op != NULL) ? op->name() : "no vm operation");
duke@1 372 }
duke@1 373
duke@1 374 RuntimeService::record_safepoint_synchronized();
duke@1 375 if (PrintSafepointStatistics) {
duke@1 376 update_statistics_on_sync_end(os::javaTimeNanos());
duke@1 377 }
duke@1 378
duke@1 379 // Call stuff that needs to be run when a safepoint is just about to be completed
duke@1 380 do_cleanup_tasks();
xlu@5042 381
xlu@5042 382 if (PrintSafepointStatistics) {
xlu@5042 383 // Record how much time spend on the above cleanup tasks
xlu@5042 384 update_statistics_on_cleanup_end(os::javaTimeNanos());
xlu@5042 385 }
duke@1 386 }
duke@1 387
duke@1 388 // Wake up all threads, so they are ready to resume execution after the safepoint
duke@1 389 // operation has been carried out
duke@1 390 void SafepointSynchronize::end() {
duke@1 391
duke@1 392 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
duke@1 393 assert((_safepoint_counter & 0x1) == 1, "must be odd");
duke@1 394 _safepoint_counter ++;
duke@1 395 // memory fence isn't required here since an odd _safepoint_counter
duke@1 396 // value can do no harm and a fence is issued below anyway.
duke@1 397
duke@1 398 DEBUG_ONLY(Thread* myThread = Thread::current();)
duke@1 399 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
duke@1 400
duke@1 401 if (PrintSafepointStatistics) {
duke@1 402 end_statistics(os::javaTimeNanos());
duke@1 403 }
duke@1 404
duke@1 405 #ifdef ASSERT
duke@1 406 // A pending_exception cannot be installed during a safepoint. The threads
duke@1 407 // may install an async exception after they come back from a safepoint into
duke@1 408 // pending_exception after they unblock. But that should happen later.
duke@1 409 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
duke@1 410 assert (!(cur->has_pending_exception() &&
duke@1 411 cur->safepoint_state()->is_at_poll_safepoint()),
duke@1 412 "safepoint installed a pending exception");
duke@1 413 }
duke@1 414 #endif // ASSERT
duke@1 415
duke@1 416 if (PageArmed) {
duke@1 417 // Make polling safepoint aware
duke@1 418 os::make_polling_page_readable();
duke@1 419 PageArmed = 0 ;
duke@1 420 }
duke@1 421
duke@1 422 // Remove safepoint check from interpreter
duke@1 423 Interpreter::ignore_safepoints();
duke@1 424
duke@1 425 {
duke@1 426 MutexLocker mu(Safepoint_lock);
duke@1 427
duke@1 428 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
duke@1 429
duke@1 430 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
duke@1 431 // when they get restarted.
duke@1 432 _state = _not_synchronized;
duke@1 433 OrderAccess::fence();
duke@1 434
rprotacio@33763 435 log_debug(safepoint)("Leaving safepoint region");
duke@1 436
duke@1 437 // Start suspended threads
duke@1 438 for(JavaThread *current = Threads::first(); current; current = current->next()) {
twisti@2131 439 // A problem occurring on Solaris is when attempting to restart threads
duke@1 440 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
duke@1 441 // to the next one (since it has been running the longest). We then have
duke@1 442 // to wait for a cpu to become available before we can continue restarting
duke@1 443 // threads.
duke@1 444 // FIXME: This causes the performance of the VM to degrade when active and with
duke@1 445 // large numbers of threads. Apparently this is due to the synchronous nature
duke@1 446 // of suspending threads.
duke@1 447 //
duke@1 448 // TODO-FIXME: the comments above are vestigial and no longer apply.
duke@1 449 // Furthermore, using solaris' schedctl in this particular context confers no benefit
duke@1 450 if (VMThreadHintNoPreempt) {
duke@1 451 os::hint_no_preempt();
duke@1 452 }
duke@1 453 ThreadSafepointState* cur_state = current->safepoint_state();
duke@1 454 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
duke@1 455 cur_state->restart();
duke@1 456 assert(cur_state->is_running(), "safepoint state has not been reset");
duke@1 457 }
duke@1 458
duke@1 459 RuntimeService::record_safepoint_end();
duke@1 460
duke@1 461 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
duke@1 462 // blocked in signal_thread_blocked
duke@1 463 Threads_lock->unlock();
duke@1 464
duke@1 465 }
jprovino@15482 466 #if INCLUDE_ALL_GCS
duke@1 467 // If there are any concurrent GC threads resume them.
duke@1 468 if (UseConcMarkSweepGC) {
duke@1 469 ConcurrentMarkSweepThread::desynchronize(false);
ysr@3262 470 } else if (UseG1GC) {
pliden@24094 471 SuspendibleThreadSet::desynchronize();
duke@1 472 }
jprovino@15482 473 #endif // INCLUDE_ALL_GCS
jwilhelm@22551 474 // record this time so VMThread can keep track how much time has elapsed
xlu@5042 475 // since last safepoint.
xlu@5042 476 _end_of_last_safepoint = os::javaTimeMillis();
duke@1 477 }
duke@1 478
duke@1 479 bool SafepointSynchronize::is_cleanup_needed() {
duke@1 480 // Need a safepoint if some inline cache buffers is non-empty
duke@1 481 if (!InlineCacheBuffer::is_empty()) return true;
duke@1 482 return false;
duke@1 483 }
duke@1 484
duke@1 485
duke@1 486
duke@1 487 // Various cleaning tasks that should be done periodically at safepoints
duke@1 488 void SafepointSynchronize::do_cleanup_tasks() {
xlu@5042 489 {
xlu@5086 490 TraceTime t1("deflating idle monitors", TraceSafepointCleanupTime);
xlu@5042 491 ObjectSynchronizer::deflate_idle_monitors();
duke@1 492 }
duke@1 493
xlu@5042 494 {
xlu@5086 495 TraceTime t2("updating inline caches", TraceSafepointCleanupTime);
xlu@5042 496 InlineCacheBuffer::update_inline_caches();
xlu@5042 497 }
iveresov@6453 498 {
iveresov@6453 499 TraceTime t3("compilation policy safepoint handler", TraceSafepointCleanupTime);
iveresov@6453 500 CompilationPolicy::policy()->do_safepoint_work();
duke@1 501 }
xlu@5042 502
coleenp@13087 503 {
anoll@20290 504 TraceTime t4("mark nmethods", TraceSafepointCleanupTime);
anoll@20290 505 NMethodSweeper::mark_active_nmethods();
coleenp@13087 506 }
coleenp@13087 507
coleenp@13087 508 if (SymbolTable::needs_rehashing()) {
coleenp@13087 509 TraceTime t5("rehashing symbol table", TraceSafepointCleanupTime);
coleenp@13087 510 SymbolTable::rehash_table();
coleenp@13087 511 }
coleenp@13087 512
coleenp@13087 513 if (StringTable::needs_rehashing()) {
coleenp@13087 514 TraceTime t6("rehashing string table", TraceSafepointCleanupTime);
coleenp@13087 515 StringTable::rehash_table();
coleenp@13087 516 }
minqi@9990 517
coleenp@24457 518 {
coleenp@24457 519 // CMS delays purging the CLDG until the beginning of the next safepoint and to
coleenp@24457 520 // make sure concurrent sweep is done
coleenp@24457 521 TraceTime t7("purging class loader data graph", TraceSafepointCleanupTime);
coleenp@24457 522 ClassLoaderDataGraph::purge_if_needed();
coleenp@24457 523 }
duke@1 524 }
duke@1 525
duke@1 526
duke@1 527 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
duke@1 528 switch(state) {
duke@1 529 case _thread_in_native:
duke@1 530 // native threads are safe if they have no java stack or have walkable stack
duke@1 531 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
duke@1 532
duke@1 533 // blocked threads should have already have walkable stack
duke@1 534 case _thread_blocked:
duke@1 535 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
duke@1 536 return true;
duke@1 537
duke@1 538 default:
duke@1 539 return false;
duke@1 540 }
duke@1 541 }
duke@1 542
duke@1 543
never@11637 544 // See if the thread is running inside a lazy critical native and
never@11637 545 // update the thread critical count if so. Also set a suspend flag to
never@11637 546 // cause the native wrapper to return into the JVM to do the unlock
never@11637 547 // once the native finishes.
never@11637 548 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
never@11637 549 if (state == _thread_in_native &&
never@11637 550 thread->has_last_Java_frame() &&
never@11637 551 thread->frame_anchor()->walkable()) {
never@11637 552 // This thread might be in a critical native nmethod so look at
never@11637 553 // the top of the stack and increment the critical count if it
never@11637 554 // is.
never@11637 555 frame wrapper_frame = thread->last_frame();
never@11637 556 CodeBlob* stub_cb = wrapper_frame.cb();
never@11637 557 if (stub_cb != NULL &&
never@11637 558 stub_cb->is_nmethod() &&
never@11637 559 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
never@11637 560 // A thread could potentially be in a critical native across
never@11637 561 // more than one safepoint, so only update the critical state on
never@11637 562 // the first one. When it returns it will perform the unlock.
never@11637 563 if (!thread->do_critical_native_unlock()) {
never@11637 564 #ifdef ASSERT
never@11637 565 if (!thread->in_critical()) {
david@35492 566 GCLocker::increment_debug_jni_lock_count();
never@11637 567 }
never@11637 568 #endif
never@11637 569 thread->enter_critical();
never@11637 570 // Make sure the native wrapper calls back on return to
never@11637 571 // perform the needed critical unlock.
never@11637 572 thread->set_critical_native_unlock();
never@11637 573 }
never@11637 574 }
never@11637 575 }
never@11637 576 }
never@11637 577
never@11637 578
never@11637 579
duke@1 580 // -------------------------------------------------------------------------------------------------------
duke@1 581 // Implementation of Safepoint callback point
duke@1 582
duke@1 583 void SafepointSynchronize::block(JavaThread *thread) {
duke@1 584 assert(thread != NULL, "thread must be set");
duke@1 585 assert(thread->is_Java_thread(), "not a Java thread");
duke@1 586
duke@1 587 // Threads shouldn't block if they are in the middle of printing, but...
duke@1 588 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
duke@1 589
duke@1 590 // Only bail from the block() call if the thread is gone from the
duke@1 591 // thread list; starting to exit should still block.
duke@1 592 if (thread->is_terminated()) {
duke@1 593 // block current thread if we come here from native code when VM is gone
duke@1 594 thread->block_if_vm_exited();
duke@1 595
duke@1 596 // otherwise do nothing
duke@1 597 return;
duke@1 598 }
duke@1 599
duke@1 600 JavaThreadState state = thread->thread_state();
duke@1 601 thread->frame_anchor()->make_walkable(thread);
duke@1 602
duke@1 603 // Check that we have a valid thread_state at this point
duke@1 604 switch(state) {
duke@1 605 case _thread_in_vm_trans:
duke@1 606 case _thread_in_Java: // From compiled code
duke@1 607
duke@1 608 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
duke@1 609 // we pretend we are still in the VM.
duke@1 610 thread->set_thread_state(_thread_in_vm);
duke@1 611
duke@1 612 if (is_synchronizing()) {
duke@1 613 Atomic::inc (&TryingToBlock) ;
duke@1 614 }
duke@1 615
duke@1 616 // We will always be holding the Safepoint_lock when we are examine the state
duke@1 617 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
duke@1 618 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
duke@1 619 Safepoint_lock->lock_without_safepoint_check();
duke@1 620 if (is_synchronizing()) {
duke@1 621 // Decrement the number of threads to wait for and signal vm thread
duke@1 622 assert(_waiting_to_block > 0, "sanity check");
duke@1 623 _waiting_to_block--;
duke@1 624 thread->safepoint_state()->set_has_called_back(true);
duke@1 625
never@12108 626 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
never@11631 627 if (thread->in_critical()) {
never@11631 628 // Notice that this thread is in a critical section
never@11631 629 increment_jni_active_count();
never@11631 630 }
never@11631 631
duke@1 632 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
duke@1 633 if (_waiting_to_block == 0) {
duke@1 634 Safepoint_lock->notify_all();
duke@1 635 }
duke@1 636 }
duke@1 637
duke@1 638 // We transition the thread to state _thread_blocked here, but
duke@1 639 // we can't do our usual check for external suspension and then
duke@1 640 // self-suspend after the lock_without_safepoint_check() call
duke@1 641 // below because we are often called during transitions while
duke@1 642 // we hold different locks. That would leave us suspended while
duke@1 643 // holding a resource which results in deadlocks.
duke@1 644 thread->set_thread_state(_thread_blocked);
duke@1 645 Safepoint_lock->unlock();
duke@1 646
duke@1 647 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
duke@1 648 // the entire safepoint, the threads will all line up here during the safepoint.
duke@1 649 Threads_lock->lock_without_safepoint_check();
duke@1 650 // restore original state. This is important if the thread comes from compiled code, so it
duke@1 651 // will continue to execute with the _thread_in_Java state.
duke@1 652 thread->set_thread_state(state);
duke@1 653 Threads_lock->unlock();
duke@1 654 break;
duke@1 655
duke@1 656 case _thread_in_native_trans:
duke@1 657 case _thread_blocked_trans:
duke@1 658 case _thread_new_trans:
duke@1 659 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
duke@1 660 thread->print_thread_state();
duke@1 661 fatal("Deadlock in safepoint code. "
duke@1 662 "Should have called back to the VM before blocking.");
duke@1 663 }
duke@1 664
duke@1 665 // We transition the thread to state _thread_blocked here, but
duke@1 666 // we can't do our usual check for external suspension and then
duke@1 667 // self-suspend after the lock_without_safepoint_check() call
duke@1 668 // below because we are often called during transitions while
duke@1 669 // we hold different locks. That would leave us suspended while
duke@1 670 // holding a resource which results in deadlocks.
duke@1 671 thread->set_thread_state(_thread_blocked);
duke@1 672
duke@1 673 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
duke@1 674 // the safepoint code might still be waiting for it to block. We need to change the state here,
duke@1 675 // so it can see that it is at a safepoint.
duke@1 676
duke@1 677 // Block until the safepoint operation is completed.
duke@1 678 Threads_lock->lock_without_safepoint_check();
duke@1 679
duke@1 680 // Restore state
duke@1 681 thread->set_thread_state(state);
duke@1 682
duke@1 683 Threads_lock->unlock();
duke@1 684 break;
duke@1 685
duke@1 686 default:
david@33105 687 fatal("Illegal threadstate encountered: %d", state);
duke@1 688 }
duke@1 689
duke@1 690 // Check for pending. async. exceptions or suspends - except if the
duke@1 691 // thread was blocked inside the VM. has_special_runtime_exit_condition()
duke@1 692 // is called last since it grabs a lock and we only want to do that when
duke@1 693 // we must.
duke@1 694 //
duke@1 695 // Note: we never deliver an async exception at a polling point as the
duke@1 696 // compiler may not have an exception handler for it. The polling
duke@1 697 // code will notice the async and deoptimize and the exception will
duke@1 698 // be delivered. (Polling at a return point is ok though). Sure is
duke@1 699 // a lot of bother for a deprecated feature...
duke@1 700 //
duke@1 701 // We don't deliver an async exception if the thread state is
duke@1 702 // _thread_in_native_trans so JNI functions won't be called with
duke@1 703 // a surprising pending exception. If the thread state is going back to java,
duke@1 704 // async exception is checked in check_special_condition_for_native_trans().
duke@1 705
duke@1 706 if (state != _thread_blocked_trans &&
duke@1 707 state != _thread_in_vm_trans &&
duke@1 708 thread->has_special_runtime_exit_condition()) {
duke@1 709 thread->handle_special_runtime_exit_condition(
duke@1 710 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
duke@1 711 }
duke@1 712 }
duke@1 713
duke@1 714 // ------------------------------------------------------------------------------------------------------
duke@1 715 // Exception handlers
duke@1 716
duke@1 717
duke@1 718 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
duke@1 719 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
duke@1 720 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
duke@1 721 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
duke@1 722
duke@1 723 if (ShowSafepointMsgs) {
duke@1 724 tty->print("handle_polling_page_exception: ");
duke@1 725 }
duke@1 726
duke@1 727 if (PrintSafepointStatistics) {
duke@1 728 inc_page_trap_count();
duke@1 729 }
duke@1 730
duke@1 731 ThreadSafepointState* state = thread->safepoint_state();
duke@1 732
duke@1 733 state->handle_polling_page_exception();
duke@1 734 }
duke@1 735
duke@1 736
duke@1 737 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
duke@1 738 if (!timeout_error_printed) {
duke@1 739 timeout_error_printed = true;
jwilhelm@22551 740 // Print out the thread info which didn't reach the safepoint for debugging
duke@1 741 // purposes (useful when there are lots of threads in the debugger).
drchase@24424 742 tty->cr();
duke@1 743 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
duke@1 744 if (reason == _spinning_timeout) {
duke@1 745 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
duke@1 746 } else if (reason == _blocking_timeout) {
duke@1 747 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
duke@1 748 }
duke@1 749
duke@1 750 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
duke@1 751 ThreadSafepointState *cur_state;
duke@1 752 ResourceMark rm;
duke@1 753 for(JavaThread *cur_thread = Threads::first(); cur_thread;
duke@1 754 cur_thread = cur_thread->next()) {
duke@1 755 cur_state = cur_thread->safepoint_state();
duke@1 756
duke@1 757 if (cur_thread->thread_state() != _thread_blocked &&
duke@1 758 ((reason == _spinning_timeout && cur_state->is_running()) ||
duke@1 759 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
duke@1 760 tty->print("# ");
duke@1 761 cur_thread->print();
drchase@24424 762 tty->cr();
duke@1 763 }
duke@1 764 }
duke@1 765 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
duke@1 766 }
duke@1 767
duke@1 768 // To debug the long safepoint, specify both DieOnSafepointTimeout &
duke@1 769 // ShowMessageBoxOnError.
duke@1 770 if (DieOnSafepointTimeout) {
duke@1 771 VM_Operation *op = VMThread::vm_operation();
david@33105 772 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
david@33105 773 SafepointTimeoutDelay,
david@33105 774 op != NULL ? op->name() : "no vm operation");
duke@1 775 }
duke@1 776 }
duke@1 777
duke@1 778
duke@1 779 // -------------------------------------------------------------------------------------------------------
duke@1 780 // Implementation of ThreadSafepointState
duke@1 781
duke@1 782 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
duke@1 783 _thread = thread;
duke@1 784 _type = _running;
duke@1 785 _has_called_back = false;
duke@1 786 _at_poll_safepoint = false;
duke@1 787 }
duke@1 788
duke@1 789 void ThreadSafepointState::create(JavaThread *thread) {
duke@1 790 ThreadSafepointState *state = new ThreadSafepointState(thread);
duke@1 791 thread->set_safepoint_state(state);
duke@1 792 }
duke@1 793
duke@1 794 void ThreadSafepointState::destroy(JavaThread *thread) {
duke@1 795 if (thread->safepoint_state()) {
duke@1 796 delete(thread->safepoint_state());
duke@1 797 thread->set_safepoint_state(NULL);
duke@1 798 }
duke@1 799 }
duke@1 800
duke@1 801 void ThreadSafepointState::examine_state_of_thread() {
duke@1 802 assert(is_running(), "better be running or just have hit safepoint poll");
duke@1 803
duke@1 804 JavaThreadState state = _thread->thread_state();
duke@1 805
never@6269 806 // Save the state at the start of safepoint processing.
never@6269 807 _orig_thread_state = state;
never@6269 808
duke@1 809 // Check for a thread that is suspended. Note that thread resume tries
duke@1 810 // to grab the Threads_lock which we own here, so a thread cannot be
duke@1 811 // resumed during safepoint synchronization.
duke@1 812
dcubed@3826 813 // We check to see if this thread is suspended without locking to
dcubed@3826 814 // avoid deadlocking with a third thread that is waiting for this
dcubed@3826 815 // thread to be suspended. The third thread can notice the safepoint
dcubed@3826 816 // that we're trying to start at the beginning of its SR_lock->wait()
dcubed@3826 817 // call. If that happens, then the third thread will block on the
dcubed@3826 818 // safepoint while still holding the underlying SR_lock. We won't be
dcubed@3826 819 // able to get the SR_lock and we'll deadlock.
dcubed@3826 820 //
dcubed@3826 821 // We don't need to grab the SR_lock here for two reasons:
dcubed@3826 822 // 1) The suspend flags are both volatile and are set with an
dcubed@3826 823 // Atomic::cmpxchg() call so we should see the suspended
dcubed@3826 824 // state right away.
dcubed@3826 825 // 2) We're being called from the safepoint polling loop; if
dcubed@3826 826 // we don't see the suspended state on this iteration, then
dcubed@3826 827 // we'll come around again.
dcubed@3826 828 //
dcubed@3826 829 bool is_suspended = _thread->is_ext_suspended();
duke@1 830 if (is_suspended) {
duke@1 831 roll_forward(_at_safepoint);
duke@1 832 return;
duke@1 833 }
duke@1 834
duke@1 835 // Some JavaThread states have an initial safepoint state of
duke@1 836 // running, but are actually at a safepoint. We will happily
duke@1 837 // agree and update the safepoint state here.
duke@1 838 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
never@12108 839 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
never@11631 840 roll_forward(_at_safepoint);
never@11631 841 return;
duke@1 842 }
duke@1 843
duke@1 844 if (state == _thread_in_vm) {
duke@1 845 roll_forward(_call_back);
duke@1 846 return;
duke@1 847 }
duke@1 848
duke@1 849 // All other thread states will continue to run until they
duke@1 850 // transition and self-block in state _blocked
duke@1 851 // Safepoint polling in compiled code causes the Java threads to do the same.
duke@1 852 // Note: new threads may require a malloc so they must be allowed to finish
duke@1 853
duke@1 854 assert(is_running(), "examine_state_of_thread on non-running thread");
duke@1 855 return;
duke@1 856 }
duke@1 857
duke@1 858 // Returns true is thread could not be rolled forward at present position.
duke@1 859 void ThreadSafepointState::roll_forward(suspend_type type) {
duke@1 860 _type = type;
duke@1 861
duke@1 862 switch(_type) {
duke@1 863 case _at_safepoint:
duke@1 864 SafepointSynchronize::signal_thread_at_safepoint();
never@12108 865 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
never@12108 866 if (_thread->in_critical()) {
never@12108 867 // Notice that this thread is in a critical section
never@12108 868 SafepointSynchronize::increment_jni_active_count();
never@12108 869 }
duke@1 870 break;
duke@1 871
duke@1 872 case _call_back:
duke@1 873 set_has_called_back(false);
duke@1 874 break;
duke@1 875
duke@1 876 case _running:
duke@1 877 default:
duke@1 878 ShouldNotReachHere();
duke@1 879 }
duke@1 880 }
duke@1 881
duke@1 882 void ThreadSafepointState::restart() {
duke@1 883 switch(type()) {
duke@1 884 case _at_safepoint:
duke@1 885 case _call_back:
duke@1 886 break;
duke@1 887
duke@1 888 case _running:
duke@1 889 default:
bpittore@31592 890 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d",
david@33148 891 p2i(_thread), _type);
duke@1 892 _thread->print();
duke@1 893 ShouldNotReachHere();
duke@1 894 }
duke@1 895 _type = _running;
duke@1 896 set_has_called_back(false);
duke@1 897 }
duke@1 898
duke@1 899
duke@1 900 void ThreadSafepointState::print_on(outputStream *st) const {
goetz@33589 901 const char *s = NULL;
duke@1 902
duke@1 903 switch(_type) {
duke@1 904 case _running : s = "_running"; break;
duke@1 905 case _at_safepoint : s = "_at_safepoint"; break;
duke@1 906 case _call_back : s = "_call_back"; break;
duke@1 907 default:
duke@1 908 ShouldNotReachHere();
duke@1 909 }
duke@1 910
duke@1 911 st->print_cr("Thread: " INTPTR_FORMAT
duke@1 912 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
david@33148 913 p2i(_thread), _thread->osthread()->thread_id(), s, _has_called_back,
duke@1 914 _at_poll_safepoint);
duke@1 915
duke@1 916 _thread->print_thread_state_on(st);
duke@1 917 }
duke@1 918
duke@1 919 // ---------------------------------------------------------------------------------------------------------------------
duke@1 920
duke@1 921 // Block the thread at the safepoint poll or poll return.
duke@1 922 void ThreadSafepointState::handle_polling_page_exception() {
duke@1 923
duke@1 924 // Check state. block() will set thread state to thread_in_vm which will
duke@1 925 // cause the safepoint state _type to become _call_back.
duke@1 926 assert(type() == ThreadSafepointState::_running,
duke@1 927 "polling page exception on thread not running state");
duke@1 928
duke@1 929 // Step 1: Find the nmethod from the return address
duke@1 930 if (ShowSafepointMsgs && Verbose) {
david@33148 931 tty->print_cr("Polling page exception at " INTPTR_FORMAT, p2i(thread()->saved_exception_pc()));
duke@1 932 }
duke@1 933 address real_return_addr = thread()->saved_exception_pc();
duke@1 934
duke@1 935 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
duke@1 936 assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod");
duke@1 937 nmethod* nm = (nmethod*)cb;
duke@1 938
duke@1 939 // Find frame of caller
duke@1 940 frame stub_fr = thread()->last_frame();
duke@1 941 CodeBlob* stub_cb = stub_fr.cb();
duke@1 942 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
duke@1 943 RegisterMap map(thread(), true);
duke@1 944 frame caller_fr = stub_fr.sender(&map);
duke@1 945
duke@1 946 // Should only be poll_return or poll
duke@1 947 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
duke@1 948
duke@1 949 // This is a poll immediately before a return. The exception handling code
duke@1 950 // has already had the effect of causing the return to occur, so the execution
duke@1 951 // will continue immediately after the call. In addition, the oopmap at the
duke@1 952 // return point does not mark the return value as an oop (if it is), so
duke@1 953 // it needs a handle here to be updated.
duke@1 954 if( nm->is_at_poll_return(real_return_addr) ) {
duke@1 955 // See if return type is an oop.
duke@1 956 bool return_oop = nm->method()->is_returning_oop();
duke@1 957 Handle return_value;
duke@1 958 if (return_oop) {
duke@1 959 // The oop result has been saved on the stack together with all
duke@1 960 // the other registers. In order to preserve it over GCs we need
duke@1 961 // to keep it in a handle.
duke@1 962 oop result = caller_fr.saved_oop_result(&map);
duke@1 963 assert(result == NULL || result->is_oop(), "must be oop");
duke@1 964 return_value = Handle(thread(), result);
duke@1 965 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
duke@1 966 }
duke@1 967
duke@1 968 // Block the thread
duke@1 969 SafepointSynchronize::block(thread());
duke@1 970
duke@1 971 // restore oop result, if any
duke@1 972 if (return_oop) {
duke@1 973 caller_fr.set_saved_oop_result(&map, return_value());
duke@1 974 }
duke@1 975 }
duke@1 976
duke@1 977 // This is a safepoint poll. Verify the return address and block.
duke@1 978 else {
duke@1 979 set_at_poll_safepoint(true);
duke@1 980
duke@1 981 // verify the blob built the "return address" correctly
duke@1 982 assert(real_return_addr == caller_fr.pc(), "must match");
duke@1 983
duke@1 984 // Block the thread
duke@1 985 SafepointSynchronize::block(thread());
duke@1 986 set_at_poll_safepoint(false);
duke@1 987
duke@1 988 // If we have a pending async exception deoptimize the frame
duke@1 989 // as otherwise we may never deliver it.
duke@1 990 if (thread()->has_async_condition()) {
duke@1 991 ThreadInVMfromJavaNoAsyncException __tiv(thread());
never@7106 992 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
duke@1 993 }
duke@1 994
duke@1 995 // If an exception has been installed we must check for a pending deoptimization
duke@1 996 // Deoptimize frame if exception has been thrown.
duke@1 997
duke@1 998 if (thread()->has_pending_exception() ) {
duke@1 999 RegisterMap map(thread(), true);
duke@1 1000 frame caller_fr = stub_fr.sender(&map);
duke@1 1001 if (caller_fr.is_deoptimized_frame()) {
duke@1 1002 // The exception patch will destroy registers that are still
duke@1 1003 // live and will be needed during deoptimization. Defer the
jwilhelm@22551 1004 // Async exception should have deferred the exception until the
duke@1 1005 // next safepoint which will be detected when we get into
duke@1 1006 // the interpreter so if we have an exception now things
duke@1 1007 // are messed up.
duke@1 1008
duke@1 1009 fatal("Exception installed and deoptimization is pending");
duke@1 1010 }
duke@1 1011 }
duke@1 1012 }
duke@1 1013 }
duke@1 1014
duke@1 1015
duke@1 1016 //
duke@1 1017 // Statistics & Instrumentations
duke@1 1018 //
duke@1 1019 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
xlu@5042 1020 jlong SafepointSynchronize::_safepoint_begin_time = 0;
duke@1 1021 int SafepointSynchronize::_cur_stat_index = 0;
duke@1 1022 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
duke@1 1023 julong SafepointSynchronize::_coalesced_vmop_count = 0;
duke@1 1024 jlong SafepointSynchronize::_max_sync_time = 0;
xlu@5042 1025 jlong SafepointSynchronize::_max_vmop_time = 0;
xlu@5042 1026 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
duke@1 1027
xlu@5042 1028 static jlong cleanup_end_time = 0;
duke@1 1029 static bool need_to_track_page_armed_status = false;
duke@1 1030 static bool init_done = false;
duke@1 1031
xlu@5042 1032 // Helper method to print the header.
xlu@5042 1033 static void print_header() {
xlu@5042 1034 tty->print(" vmop "
xlu@5042 1035 "[threads: total initially_running wait_to_block] ");
xlu@5042 1036 tty->print("[time: spin block sync cleanup vmop] ");
xlu@5042 1037
xlu@5042 1038 // no page armed status printed out if it is always armed.
xlu@5042 1039 if (need_to_track_page_armed_status) {
xlu@5042 1040 tty->print("page_armed ");
xlu@5042 1041 }
xlu@5042 1042
xlu@5042 1043 tty->print_cr("page_trap_count");
xlu@5042 1044 }
xlu@5042 1045
duke@1 1046 void SafepointSynchronize::deferred_initialize_stat() {
duke@1 1047 if (init_done) return;
duke@1 1048
duke@1 1049 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
duke@1 1050 // be printed right away, in which case, _safepoint_stats will regress to
duke@1 1051 // a single element array. Otherwise, it is a circular ring buffer with default
duke@1 1052 // size of PrintSafepointStatisticsCount.
duke@1 1053 int stats_array_size;
duke@1 1054 if (PrintSafepointStatisticsTimeout > 0) {
duke@1 1055 stats_array_size = 1;
duke@1 1056 PrintSafepointStatistics = true;
duke@1 1057 } else {
duke@1 1058 stats_array_size = PrintSafepointStatisticsCount;
duke@1 1059 }
duke@1 1060 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
zgu@13195 1061 * sizeof(SafepointStats), mtInternal);
duke@1 1062 guarantee(_safepoint_stats != NULL,
duke@1 1063 "not enough memory for safepoint instrumentation data");
duke@1 1064
shade@27662 1065 if (DeferPollingPageLoopCount >= 0) {
duke@1 1066 need_to_track_page_armed_status = true;
duke@1 1067 }
duke@1 1068 init_done = true;
duke@1 1069 }
duke@1 1070
duke@1 1071 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
xlu@4006 1072 assert(init_done, "safepoint statistics array hasn't been initialized");
duke@1 1073 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1074
xlu@5042 1075 spstat->_time_stamp = _ts_of_current_safepoint;
xlu@5042 1076
duke@1 1077 VM_Operation *op = VMThread::vm_operation();
duke@1 1078 spstat->_vmop_type = (op != NULL ? op->type() : -1);
duke@1 1079 if (op != NULL) {
duke@1 1080 _safepoint_reasons[spstat->_vmop_type]++;
duke@1 1081 }
duke@1 1082
duke@1 1083 spstat->_nof_total_threads = nof_threads;
duke@1 1084 spstat->_nof_initial_running_threads = nof_running;
duke@1 1085 spstat->_nof_threads_hit_page_trap = 0;
duke@1 1086
duke@1 1087 // Records the start time of spinning. The real time spent on spinning
duke@1 1088 // will be adjusted when spin is done. Same trick is applied for time
duke@1 1089 // spent on waiting for threads to block.
duke@1 1090 if (nof_running != 0) {
duke@1 1091 spstat->_time_to_spin = os::javaTimeNanos();
duke@1 1092 } else {
duke@1 1093 spstat->_time_to_spin = 0;
duke@1 1094 }
duke@1 1095 }
duke@1 1096
duke@1 1097 void SafepointSynchronize::update_statistics_on_spin_end() {
duke@1 1098 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1099
duke@1 1100 jlong cur_time = os::javaTimeNanos();
duke@1 1101
duke@1 1102 spstat->_nof_threads_wait_to_block = _waiting_to_block;
duke@1 1103 if (spstat->_nof_initial_running_threads != 0) {
duke@1 1104 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
duke@1 1105 }
duke@1 1106
duke@1 1107 if (need_to_track_page_armed_status) {
duke@1 1108 spstat->_page_armed = (PageArmed == 1);
duke@1 1109 }
duke@1 1110
duke@1 1111 // Records the start time of waiting for to block. Updated when block is done.
duke@1 1112 if (_waiting_to_block != 0) {
duke@1 1113 spstat->_time_to_wait_to_block = cur_time;
duke@1 1114 } else {
duke@1 1115 spstat->_time_to_wait_to_block = 0;
duke@1 1116 }
duke@1 1117 }
duke@1 1118
duke@1 1119 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
duke@1 1120 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1121
duke@1 1122 if (spstat->_nof_threads_wait_to_block != 0) {
duke@1 1123 spstat->_time_to_wait_to_block = end_time -
duke@1 1124 spstat->_time_to_wait_to_block;
duke@1 1125 }
duke@1 1126
duke@1 1127 // Records the end time of sync which will be used to calculate the total
duke@1 1128 // vm operation time. Again, the real time spending in syncing will be deducted
duke@1 1129 // from the start of the sync time later when end_statistics is called.
xlu@5042 1130 spstat->_time_to_sync = end_time - _safepoint_begin_time;
duke@1 1131 if (spstat->_time_to_sync > _max_sync_time) {
duke@1 1132 _max_sync_time = spstat->_time_to_sync;
duke@1 1133 }
xlu@5042 1134
xlu@5042 1135 spstat->_time_to_do_cleanups = end_time;
xlu@5042 1136 }
xlu@5042 1137
xlu@5042 1138 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
xlu@5042 1139 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
xlu@5042 1140
xlu@5042 1141 // Record how long spent in cleanup tasks.
xlu@5042 1142 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
xlu@5042 1143
xlu@5042 1144 cleanup_end_time = end_time;
duke@1 1145 }
duke@1 1146
duke@1 1147 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
duke@1 1148 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1149
duke@1 1150 // Update the vm operation time.
xlu@5042 1151 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
xlu@5042 1152 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
xlu@5042 1153 _max_vmop_time = spstat->_time_to_exec_vmop;
xlu@5042 1154 }
duke@1 1155 // Only the sync time longer than the specified
duke@1 1156 // PrintSafepointStatisticsTimeout will be printed out right away.
duke@1 1157 // By default, it is -1 meaning all samples will be put into the list.
duke@1 1158 if ( PrintSafepointStatisticsTimeout > 0) {
gziemski@33222 1159 if (spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
duke@1 1160 print_statistics();
duke@1 1161 }
duke@1 1162 } else {
duke@1 1163 // The safepoint statistics will be printed out when the _safepoin_stats
duke@1 1164 // array fills up.
xlu@5042 1165 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
duke@1 1166 print_statistics();
duke@1 1167 _cur_stat_index = 0;
xlu@5042 1168 } else {
xlu@5042 1169 _cur_stat_index++;
duke@1 1170 }
duke@1 1171 }
duke@1 1172 }
duke@1 1173
duke@1 1174 void SafepointSynchronize::print_statistics() {
duke@1 1175 SafepointStats* sstats = _safepoint_stats;
duke@1 1176
xlu@5042 1177 for (int index = 0; index <= _cur_stat_index; index++) {
xlu@5042 1178 if (index % 30 == 0) {
xlu@5042 1179 print_header();
xlu@5042 1180 }
duke@1 1181 sstats = &_safepoint_stats[index];
xlu@5042 1182 tty->print("%.3f: ", sstats->_time_stamp);
xlu@5042 1183 tty->print("%-26s ["
bpittore@31592 1184 INT32_FORMAT_W(8) INT32_FORMAT_W(11) INT32_FORMAT_W(15)
xlu@5042 1185 " ] ",
duke@1 1186 sstats->_vmop_type == -1 ? "no vm operation" :
duke@1 1187 VM_Operation::name(sstats->_vmop_type),
duke@1 1188 sstats->_nof_total_threads,
duke@1 1189 sstats->_nof_initial_running_threads,
duke@1 1190 sstats->_nof_threads_wait_to_block);
duke@1 1191 // "/ MICROUNITS " is to convert the unit from nanos to millis.
xlu@5042 1192 tty->print(" ["
bpittore@31592 1193 INT64_FORMAT_W(6) INT64_FORMAT_W(6)
bpittore@31592 1194 INT64_FORMAT_W(6) INT64_FORMAT_W(6)
bpittore@31592 1195 INT64_FORMAT_W(6) " ] ",
duke@1 1196 sstats->_time_to_spin / MICROUNITS,
duke@1 1197 sstats->_time_to_wait_to_block / MICROUNITS,
duke@1 1198 sstats->_time_to_sync / MICROUNITS,
xlu@5042 1199 sstats->_time_to_do_cleanups / MICROUNITS,
xlu@5042 1200 sstats->_time_to_exec_vmop / MICROUNITS);
duke@1 1201
duke@1 1202 if (need_to_track_page_armed_status) {
bpittore@31592 1203 tty->print(INT32_FORMAT " ", sstats->_page_armed);
duke@1 1204 }
bpittore@31592 1205 tty->print_cr(INT32_FORMAT " ", sstats->_nof_threads_hit_page_trap);
duke@1 1206 }
duke@1 1207 }
duke@1 1208
duke@1 1209 // This method will be called when VM exits. It will first call
duke@1 1210 // print_statistics to print out the rest of the sampling. Then
duke@1 1211 // it tries to summarize the sampling.
duke@1 1212 void SafepointSynchronize::print_stat_on_exit() {
duke@1 1213 if (_safepoint_stats == NULL) return;
duke@1 1214
duke@1 1215 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1216
duke@1 1217 // During VM exit, end_statistics may not get called and in that
duke@1 1218 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
duke@1 1219 // don't print it out.
duke@1 1220 // Approximate the vm op time.
duke@1 1221 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
xlu@5042 1222 os::javaTimeNanos() - cleanup_end_time;
duke@1 1223
duke@1 1224 if ( PrintSafepointStatisticsTimeout < 0 ||
gziemski@33222 1225 spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
duke@1 1226 print_statistics();
duke@1 1227 }
drchase@24424 1228 tty->cr();
duke@1 1229
duke@1 1230 // Print out polling page sampling status.
duke@1 1231 if (!need_to_track_page_armed_status) {
shade@27662 1232 tty->print_cr("Polling page always armed");
duke@1 1233 } else {
david@33148 1234 tty->print_cr("Defer polling page loop count = " INTX_FORMAT "\n",
david@33148 1235 DeferPollingPageLoopCount);
duke@1 1236 }
duke@1 1237
duke@1 1238 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
duke@1 1239 if (_safepoint_reasons[index] != 0) {
bpittore@31592 1240 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index),
duke@1 1241 _safepoint_reasons[index]);
duke@1 1242 }
duke@1 1243 }
duke@1 1244
bpittore@31592 1245 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint",
duke@1 1246 _coalesced_vmop_count);
bpittore@31592 1247 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms",
duke@1 1248 _max_sync_time / MICROUNITS);
xlu@5042 1249 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
bpittore@31592 1250 INT64_FORMAT_W(5) " ms",
xlu@5042 1251 _max_vmop_time / MICROUNITS);
duke@1 1252 }
duke@1 1253
duke@1 1254 // ------------------------------------------------------------------------------------------------
duke@1 1255 // Non-product code
duke@1 1256
duke@1 1257 #ifndef PRODUCT
duke@1 1258
duke@1 1259 void SafepointSynchronize::print_state() {
duke@1 1260 if (_state == _not_synchronized) {
duke@1 1261 tty->print_cr("not synchronized");
duke@1 1262 } else if (_state == _synchronizing || _state == _synchronized) {
duke@1 1263 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
duke@1 1264 "synchronized");
duke@1 1265
duke@1 1266 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
duke@1 1267 cur->safepoint_state()->print();
duke@1 1268 }
duke@1 1269 }
duke@1 1270 }
duke@1 1271
duke@1 1272 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
duke@1 1273 if (ShowSafepointMsgs) {
duke@1 1274 va_list ap;
duke@1 1275 va_start(ap, format);
duke@1 1276 tty->vprint_cr(format, ap);
duke@1 1277 va_end(ap);
duke@1 1278 }
duke@1 1279 }
duke@1 1280
duke@1 1281 #endif // !PRODUCT